I've gone thru many of the threads, but started falling asleep after the 11th page...

I have 147,000 miles on my 2004 Expedition, Eddie Bauer edition, with heavy duty tow package. 2 years ago I could pull 3400lbs of hay on my flat bed car carrier and not feel my load. Now, my beloved steel steed seems to labor going up hills. I took 'Rose' to my local Army instillation Auto Care Center but they couldn't find anything wrong. I have also noticed that my mileage has decrease, not significantly, but still down from 15mpg to 11 mpg when I tow.

My husband replaced the spark plugs in the summer before he deployed and I have the oil changed regularly. What else could be causing her to struggle? Age? She doesn't smoke and there's no beer belly...

 

My guess and only a guess would be dirty air filter, bad gas or needs a tuneup (plugs, cap, rotor and wires). Make sure tires are aired up too.

 

The Post Auto Hobby Shop or the AAFES (BX) Auto Care Center probably doesn't have to correct diagnostic tools to properly diagnose your Ford. Your Ford is an electronic marvel with all sorts of electronic gizmos and sensors. It requires very specialized diagnostic equipment to properly diagnose problems with any late-model vehicle. I'd take it to a Ford dealer and ask for an electronic diagnosis. They'll probably charge you about $100 just to hook up your SUV to the electronic diagnostic equipment and read the codes. But then they could tell you what, if anything, is wrong with your SUV and give you a good estimate as to the cost to fix it.

Your 2004 probably has electronic ignition, so it doesn't have a distributor cap or rotor. Changing the spark plugs is about all you can do for a "tuneup" on a gasoline engine that has electronic ignition. Spark plug wires? Well, yeah, on old jalopies, but I wouldn't suspect the ignition wires on a 2004. But be certain the air filter is clean and no unfiltered air can get past it and into the engine. Also be certain the emissions equipment is all working as designed. The electronic diagnosis will tell you if you have problems with your emissions equipment or ignition wires or anything else that could cause your Ford to loose power and torque.

 

With that kind of mileage, you're probably looking at a stopped up catalytic convertor, bad O2 sensors or even both.